This invention relates to injection molding and more particularly to a valve gated system for making plastic products with a gas filled central portion.
Molding hollow plastic products by injecting pressurized gas in the center of a stream of melt is described in U.S. Pat. No. 4,101,617 to Friederich which issued July 18, 1978. However, this previous arrangement has the disadvantage, particularly for large size products which require a larger diameter gate, that the gate cannot be shut off. Consequently melt drooling when the mold opens and increased cycle time become problems.